1. Field of the Invention
The present invention relates generally to a water purification and treatment apparatus, and in particular to a water purification and treatment apparatus and a water purification and treatment process using a combination of sedimentation, filtration, and bio-contact aeration processes.
2. The Prior Arts
The purpose of purifying and treating raw water, sewage or wastewater is, in general, to improve water quality to reach the standard for fresh drinking, or the standard for discharging. As to the former, a reverse osmosis process is commonly used no matter what is the source of water to be purified, which may be, for example, seawater, river water, well water or rainwater. As to the latter, based on the source of sewage or wastewater to be purified, an anaerobic chemical treatment process, an aerobic activated sludge process, a bio-contact aeration process and the like, or a combination thereof may be used to purify the water to reach the standard for discharging. For example, the sewage or wastewater discharged from a stock farm is often treated using a chemical coagulating sedimentation process, together with an activated sludge process or a bio-contact aeration process.
However, whether a reverse osmosis process is used to purify raw water, or a chemical coagulating sedimentation process is used to purify sewage or wastewater discharged from various industries, although some extent of purification effect can be realized, chemicals must be used. Over a long time of treatment, large amounts of chemicals will be consumed, at the same time, more sludge will be produced and may be noxious due to residual chemicals contained therein, which thereby can not be utilized directly as organic fertilizer, and also is not suitable to be buried directly, but should be further disposed, resulting in the increase of disposal costs. Further, the efficiency of water purification is limited by using the above processes. For example, as to the reverse osmosis process, the output of treated water suitable for fresh drinking is only about 30% of input water, and the wastewater generated is up to be 70%.
Additionally, the activated sludge process has many advantages, such as being environmental-friendly, substrates being mixed uniformly, good operability and low apparatus costs. But, a conventional activated sludge aeration basin can not provide sufficient dissolved oxygen amount because the sludge will be restricted in limited aeration time and space duration its treatment, especially as large amounts of microorganisms propagate in the water and consume much dissolved oxygen in the water. Therefore, if aeration amount in unit time and temperature control are not operated appropriately, many microorganisms will die rapidly. Accordingly, it is required to perform reducing volume treatment to the expanded sludge, which, on the contrary, results the sludge to be a pollution source. It is not suitable for treating lots of sewage and wastewater. As to the bio-contact aeration process, which is improved based on the activated sludge process, has the advantages in that microorganisms are abundant, sludge is less, and sedimentation is easy relatively, but also has advantages in that filtering materials are easy to be blocked by residuals, difficult to be cleaned, and lack of operation flexibility, therefore it is also economic.
A combination of activated sludge process and a bio-contact aeration process is proposed to treat wastewater and sewage discharged from a slaughterhouse, which can reduce ⅓ sludge amount as compared with a simple activated sludge process. But, when much more sewage and wastewater is treated, the sludge amount generated is still very annoying and need to be further reduced in volume. Therefore, in an existing water treatment apparatus, due to the restriction of further treatment of sludge, a settling basin equipped therewith at most only can treat 500˜2000 Kg water. Treatment scale will be somewhat limited.
Raw water, which can be treated by the reverse osmosis process, relatively has little foreign materials or less pollution. However, as an example of river water or well water, once at the previous treatment stage it is required to perform the steps of sand stones and foreign materials removing, bacteria killing, chlorine removing, coagulating sedimentation, and cleaning. In addition, due to influence of industrial wastewater and polluted air, the saw water also contains much heavy metal therein. Therefore, even though the raw water is ocean water, besides salts contained therein, the concentration of mercury and lead is also high, and those can not be removed by the reverse osmosis process over a long time of period.
In addition, a conventional circular settling basin uses the principle that the heavier sludge settles rapidly to discharge the settled sludge through a discharging outlet, rather than uses a sludge scrapping device. Therefore, the sludge around the discharging outlet may be unable to be discharged out successfully, but settled and accumulated there gradually. Further, since a water inlet and a water outlet both are positioned above the basin, even the sludge can be settled to some extent due to its higher specific density, the output water will also contains some sludge. The apparatus also has the disadvantages of short life time, high maintenance costs and uneconomic.
As to a conventional square basin having a sludge scrapping device, the device operates reciprocally, therefore each sludge scrapping cycle has an idle stoke of wasted time. Therefore, in summarization of the above apparatuses, they all has the disadvantages of short life time, high maintenance costs and uneconomic.